A record number of candidates are running for Congress this year, a surge in political involvement at a time of fierce liberal opposition to President Trump and sustained levels of voter disgust toward the performance of lawmakers inside the Capitol.

By Dec. 31, 2017, more than 2,100 people had taken at least the first step toward running for the House or Senate by filing the necessary paperwork, according to records kept by the Federal Election Commission. For context, that’s almost twice as many candidates who launched congressional campaigns in 2015. It represents the most candidates at this stage of the election season since the FEC started keeping these records, in 1977.

Democrats, particularly those running for House seats, are driving this never-before-seen gusher, adding to their hopes of picking up the 24 seats needed to win back the majority in the November midterm elections.

By Dec. 31, some 1,133 candidates had filed to run as Democrats for House seats, easily the largest crop either party has ever assembled at that point of an election cycle.

While the total number of Senate candidates is up slightly over recent history, potential candidates clearly view the House as a more realistic entry point, particularly first-timers.

Even Republicans, with 689 declared candidates for the House in 2017, have their second-largest field ever, trailing only 2009. That massive crop of 745 candidates, the second-largest ever for any party, set the stage for the 2010 midterm wave that delivered Republicans the House majority.

Of course, some of these candidates will barely field a real campaign — FEC officials say some people mockingly file paperwork for their pets.

But there is no question that the Democratic energy also has created a financial boost. Of those Democrats who declared to run for the House, 920 have filed financial reports with the FEC, compared with 558 Republicans.

Overall, Democratic House candidates raised $311 million last year, almost twice as much as Democrats had ever raised in an off year. They also raised a combined $63 million more than all House GOP candidates.

Republicans are counting on these Democrats to spend the next seven months ripping one another apart in primary campaigns that could divide the party heading into the general election. They point to the bitter reaction when the DCCC waded into a large primary field for a Texas race by attacking Laura Moser, who is mounting a liberal campaign that some strategists fear is out of step with the suburban Houston district.

The primary is Tuesday, but the fallout was immediate. Our Revolution, a political action committee associated with Sen. Bernie Sanders (I-Vt.), endorsed Moser, who is airing an ad attacking the “establishment” for trying to choose winners.

“It always backfires,” said Matt Gorman, spokesman for the National Republican Congressional Committee. He said the DCCC was playing favorites in other races, as well, which could turn the energy of all these candidates into bitter feuds.

“It really doesn’t matter how many people run because they handpick their candidates,” Gorman said.

Democrats say the energy from such widespread interest in challenging Trump and his congressional majority will outweigh the downside of some competitive primaries.

“The net benefit to us — this many candidates raising this much money — far exceeds the harm that could be done,” Heck said.

Many of these Democrats are “self-starters,” as Heck calls them, people who are willing to take a chance that they otherwise might never have taken.

Consider Lisa Brown, a former state Senate majority leader, who resigned as chancellor of Washington State University in Spokane in the summer to launch a campaign against Rep. Cathy McMorris Rodgers (Wash.), the highest-ranking Republican woman in congressional leadership.

Democrats last held the eastern Washington district in 1994, when the sitting speaker, Tom Foley, lost in a shocking upset. It has grown only more Republican and was not on anyone’s list of potential Democratic takeovers a year ago.

But Brown raised more than $600,000 in five months and has 2,000 volunteers, placing the race on the watch list of independent handicappers.

The number of candidates will only grow because many states have filing deadlines later in the spring. For example, Mallory Hagan, the 2013 Miss America, quit her job in local TV news last month to run against Rep. Mike D. Rogers (R-Ala.), whose smallest victory margin in his past four races was 19 percentage points.

“Self-starter,” Heck said of the 29-year-old.

Democrats are not expecting a victory from Hagan, but they would rather have these long-shot candidacies than not, just in case. That’s what has happened in southwestern Pennsylvania, where Democrat Conor Lamb is in a toss-up race for a House special election in a district for which the party did not even field a nominee in 2016.

The DCCC gave Lamb some counsel, but they let him make his own decision, and he has largely created a campaign apparatus of his own rather than loading up on staff from Washington.

The special election there, along with four other close contests last year in districts Trump won, has expanded the map of competitive races deep into Republican territory. Inside Elections and the Cook Political Report, independent forecasters, rate 57 and 75 GOP seats as potentially vulnerable, respectively, a number that is likely to grow as the election draws closer.

Each has fewer than 20 Democratic seats as possibly competitive.

Democrats now say that they can put a little more than 100 Republican seats in play, and they have at least one good candidate in all but three or four of those races. It remains to be seen how many of those Democrats can run quality campaigns, but there is no question that the sheer number is astounding.

And more are coming.

“We’re not going to stop recruiting until the filing period is over in every state,” Heck said.

Paul KanePaul Kane is The Washington Post's senior congressional correspondent and columnist. His column about the 115th Congress, @PKCapitol, appears throughout the week and on Sundays. He joined The Post in 2007. Follow